Soil sealing for computation of water tariffs

Project idea and background

The project idea is to develop soil sealing products based on satellite data of various resolutions to be used as input into computational models for progressive water tariffs.
A new law concerning water tariffs has been passed in Sweden. From now on, the user’s impact on the water supply systems – as well as actual use – will determine how water tariffs are applied to the property owners. This means, for example, that a property owner whose land area consists of mostly hard surfaces, such as asphalt or buildings (roofs) - and thus adds significant storm water runoff to the sewage system - will pay more than one whose property consists of vegetated areas with a high infiltration rates. The law is to go into effect on January 1, 2009.
Urbanization increases surface runoff, by increasing the amount of impervious surfaces, such as pavement and buildings, which impede the percolation of water into the aquifer. The water instead flows directly into streams or storm water runoff drains. Customarily, the storm water tax has been based on a quota of potable water used. With the passage of the new law, this method of taxation is non-compliant. Additionally, the current taxation practices do not encourage conservation since dischargers face no financial consequence of heavy use. 


The project will be carried out in close cooperation between the user, Göteborg Vatten, City of Göteborg (Gothenburg), and the remote sensing consultant, Metria. Existing methods and services for creating soil sealing products using different satellite sensors will be homogenized during the project based on user specifications and evaluations. Both pixel based and object methods will be evaluated. This study includes evaluation of several products:
• VHR mapping: 1*1km (1m resolution) and 5*5km (4m) surrounding the reference area,
• SPOT mapping 10m: The whole municipality of Göteborg,
• Soil sealing 20m: The whole municipality of Göteborg.
Input data are except from VHR and SPOT-5 satellite data also ancillary map data such as road network and building outlines, overview map information with forest, open and arable land etc.
Soil sealing map over the city of Sundsvall, year 2008.© Sara Wiman

Project goals

The project goal is to define the quality and usability of EO based soil sealing products for the calculation of water tariffs. Four different image resolutions in the range 1-20m will be evaluated. These results can also be a first step in a future development for more complicated hydraulic modeling. 


Sara Wiman, Metria (, +46 8 579 972 84,
Johan Karmalm, Göteborg Vatten, +46 31 368 70 19,

Senast uppdaterad: 29 maj 2009